"We found a global high rate of axial symptoms development during the course of follow-up, with a progressive lessening of both medication and stimulation effectiveness, and a global reduction in the synergistic effect of the ‘stimulation on/medication/on’ condition," the authors wrote. Other studies have suggested that this decline is a combination of the disease’s natural course and a decrease in response to dopaminergic therapy.
Dementia, depression, and hallucinations also became increasingly common over the follow-up period. After more than 7 years of follow-up, six patients required medication for depression, nine required medication for hallucinations, and six developed dementia.
"Our main findings suggest that, in spite of the prior clinical evolution and the young age at onset, non-levodopa-responsive symptoms progressively emerged" beyond 20 years of disease, the authors said. "In fact, at 30 years from the disease onset, more than 70% of subjects showed dementia, falls, dysphagia, or urinary incontinence."
None of the authors had any relevant disclosures.